634
Data Control Instructions Section 3-17
Note (1) When the unit is designated as 1, the range is from 1 to 8,191 times the
period. When the unit is designated as 9, the range is from 0.1 to 819.1 s.
When 9 is designated, set the integral and derivative times to within a
range of 1 to 8,191 times the sampling period.
(2) Setting the 2-PID parameter (
α) to 000 yields 0.65, the normal value.
When the manipulated variable output limit control is enabled (i.e., set to
“1”), set the values as follows:
0000
≤ MV output lower limit ≤ MV output upper limit ≤ Max. value of output
range
Example 1:
Interrupting PID Control to
Perform Autotuning
At the rising edge of CIO 0.00 (OFF to ON), the work area in D211 to D240 is
initialized according to the parameters (shown below) set in D200 to D208.
After the work area has been initialized, PID control is executed and the
manipulated variable is output to CIO 2000.
While CIO 0.00 is ON, PID control is executed at the sampling period intervals
according to the parameters set in D200 to D210. The manipulated variable is
output to CIO 2000.
The PID constants used in PID calculations will not be changed even if the
proportional band (P), integral constant (Tik), or derivative constant is
changed after CIO 0.00 turns ON.
At the rising edge of W 0.00 (OFF to ON), SETB(532) turns ON bit 15 of D209
(C+9) and starts autotuning. When autotuning is completed, the calculated P,
I, and D constants are written to C+1, C+2, and C+3. PID control is then
restarted with the new PID constants.
Bits 00 to 11
of C+9
AT Calculation Gain Set this parameter to adjust the
contribution of the PID calcula-
tion results to the stored values.
Normally, leave this parameter
set to its default (0000).
• Increase the value when
emphasizing stability.
• Decrease the value when
emphasizing responsiveness.
0000 hex: 1.00 (Default)
0001 to 03E8 hex (1 to 1000);
(0.01 to 10.00, in units of 0.01)
Allowed
(These param-
eters are read
when autotun-
ing starts.)
C+10 Limit-cycle Hystere-
sis
Sets the hysteresis when the
limit cycle is generated. The
default setting for reverse opera-
tion turns ON the MV with a hys-
teresis of SV−20%.
Increase this setting if a proper
limit cycle cannot be generated
because the PV is unstable.
However, the AT accuracy will
decline if the Limit-cycle Hyster-
esis is higher than necessary.
0000 hex: 0.20% (Default)
0001 to 03E8 hex:
0.01 to 10.00% in units of 0.01%
FFFF hex: 0.00%
Note The percentage is with
respect to the input range.
Control
data
Item Contents Setting range Change with
ON input
condition
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